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Examination of In-Service Coating Degradation in Gas Turbine Blades Using a Small Punch Testing Method

Published online by Cambridge University Press:  10 February 2011

J. Kameda ,
T. E. Bloomer ,
C. R. Gold ,
Y. Sugita ,
M. Ito  and
S. Sakurai
J. Kameda
Affiliation:
Center for Advanced Technology Development, Iowa State University, Ames, IA 50011
T. E. Bloomer
Affiliation:
Center for Advanced Technology Development, Iowa State University, Ames, IA 50011
C. R. Gold
Affiliation:
Center for Advanced Technology Development, Iowa State University, Ames, IA 50011
Y. Sugita
Affiliation:
Mechanical Engineering Research Laboratory, Hitachi Ltd., Hitachi, 317, Japan
M. Ito
Affiliation:
Electric Power R & D Center, Chubu Electric Power Co., Inc., Nagoya, 458, Japan.
S. Sakurai
Affiliation:
Mechanical Engineering Research Laboratory, Hitachi Ltd., Hitachi, 317, Japan
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Abstract

This paper describes examination of in-service coating degradation in land based gasturbine blades by means of a small punch testing (SP) method and scanning Auger microprobe(SAM). SP tests on coated specimens with unpolished surfaces indicated large variations ofthe mechanical properties because of the surface roughness and curvature in gas turbine blades, SP tests on polished specimens better characterized the mechanical degradation of bladecoatings. The coated specimens greatly softened and the room temperature ductility of thecoatings and substrates tended to decrease with increasing operation time. The ductile-brittletransition temperature of the coatings shifted to higher temperatures during the bladeoperation. From SAM analyses on fracture surfaces of unused and used blades, it has beenshown that oxidation and sulfidation near the coating surface, which control the fractureproperties, result from high temperature environmental attack.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 434: Symposium U – Layered Materials for Structural Applications , 1996 , 39
Copyright
Copyright © Materials Research Society 1996

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